1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a blue phase mode liquid crystal display device and a method of manufacturing the same.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device is categorized into a VA (vertical alignment) type LCD, IPS (in-plane switching) type LCD, and the like. The IPS type LCD device has advantage of wide viewing angles.
A nematic liquid crystal, a smetic liquid crystal, a cholesteric liquid crystal and the like are used as a liquid crystal of the LCD device. Among these liquid crystals, the nematic liquid crystal is widely used. However, response speed of the nematic liquid crystal is slow, and this causes degradation of display quality due to residual images.
To solve the problem, suggested is an LCD device using a blue phase mode liquid crystal, which is referred to as a blue phase mode LCD device. Optical property of the blue phase mode liquid crystal changes from isotropic property into anisotropic property by a voltage (i.e., an electric field) applied to the blue phase liquid crystal. Further, anisotropic refractive index is varied in proportion to the square of the applied voltage. Accordingly, response speed becomes fast.
The blue phase mode liquid crystal is operated by an in-plane electric field i.e., a horizontal electric field. However, when the blue phase mode LCD device displays a dark state (i.e., dark image), light leakage occurs and this causes reduction of contrast ratio.
FIG. 1 shows simulation results of optical property of the related art blue phase mode LCD device in displaying dark state.
Referring to FIG. 1, in the dark state, light leakage is great at diagonal directions i.e., 45°, 135°, 225° and 315° directions, and brightness thus increases. Therefore, contrast ratio is reduced, and display quality is thus degraded.